Permeability tuning



Jan. 21, 1941. CANQN AL 2,229,404

PERIJEABILITY TUNING Filed Jan. 3, 1939 2 Sheets-Sheet l Jan. 21, 1941.CAN-0N ETAL 2,229,404-

PERMEABILITY TUNING Filed Jan. 5, 1939 2 Sheets-Sheet 2 Patented Jan.21, 1941 UNITED STATES FATE i QEFFECE PERMEABILITY TUNING ApplicationJanuary 3, 1939, Serial No. 243,951

5 Claims.

An object of this invention is to provide an improved, simplified andconcise form of permeability ttming device for radio receiving sets-withparticular reference to the reception of broad- 5 cast frequencies.

Another object is the provision of means for readily adjusting thetuning elements to overcome small inaccuracies of manufacture withoutthe use of trimmer condensers.

10 Still another object is to provide means other than variablecondensers for simultaneously tuning two tuned stages of radiofrequency, one of which is preferably an oscillator stage.

Another object is to provide such a radio re- 15 ceiver which isoperated by push buttons, one

for each frequency it is desired to receive.

These and other objects, as will hereinafter appear, are accomplished bythis invention which is fully described in the following specification20 and shown in the accompanying drawings, in

which Figure 1 is a wiring diagram of one embodiment of the invention;

Fig. 2 is an end elevation of a frame with the 25 selector andoscillator coils mounted therein together with the switches foroperating these coils;

Fig. 3 is a partial enlarged longitudinal section through the coils;

30 Fig. 4 is a partial section on the line 4-4 of Fig. 3;

Fig. 5 is a partial section on the line 55 of Fig.

Fig. 6 is a reduced perspective view of the 35 adjusted bracket of Figs.3 and 4;

Fig. 7 is a partial perspective view of the upstruck tongue for holdingthe bracket in place; and

Fig. 8 is a reduced perspective view of a spring 40 for retaining theinsulating sleeve on the bracket.

The embodiment illustrated, particularly in Fig. 1, comprises a seriesof selector coils I I0 I0 etc. and a corresponding series of oscillatorcoils Il M I 1, etc. which are wired so as to 45 be selectivelyconnected in pairs as m and ll in a superheterodyne receiver, each pairbeing controlled as by switches operated by a push button, and thetuning of each pair of coils being controlled by mechanically connectedmagnetic 50 dust cores, all as will later be described.

The selector coils lfl [0 l0, etc. are connected at one end to a commongrounded lead 12, the other ends being connected respectively throughswitches I 3*, l3, l3, etc. to a lead I4 55 which is connected to thecontrol grid of a. first detector tube iii, with a condenser I6 acrossthe leads l2, M whereby any one of the selector coils may be operablyconnected by means of its switch to this condenser to form a resonantcircuit for a predetermined broadcast frequency. The lead M connectsthrough a condenser H and a lead It to an aerial It with a coil 20 andcondenser 2! connected to the aerial and to ground.

The oscillator coils Il Il H etc. are connected at one side to groundthrough a wire 22 and at the other through a series of switches 23 2323, etc. to a lead 24 which connects through a condenser 25 with thegrid of an oscillator tube 25. Each of the switches 23 23 23, isoperatively connected to the corresponding switch I3 13', I55 etc. asindicated by dotted lines so that these switches open and close in pairsas will later be described in detail. The lead 24 also connects toground through a tuner tracking coil 2'! and a condenser 28. The cathodeof the first detector tube I5 is connected through a lead 29 to thecathode of the oscillator tube and by a lead 30 to the top on the tunertracking coil 21. The lead 30 also connects to the 25 grid of theoscillator tube through a biasing resistance 3|.

The plate of the oscillator tube 26 is connected by a lead 32 with thescreen grid of the first detector tube l5 Amplification is then obtained30 in any well known manner by means of an intermediate frequencyamplifying circuit 40 and is connected to a second detector and audiofrequency (not shown) amplifier and thence to a loud speaker. 35

Much of the novelty in this invention resides in the construction andarrangement of the selector coils Hi In It, etc. and of the oscillatorcoils Il li H etc. These will now be described in detail. It will beunderstood however that where one of the selector coils as Ill is tunedwith respect to the condenser Hi to a particular broadcast frequency,the corresponding oscillator coil H will be tuned to this same frequencyplus the intermediate frequency. The first detector is then tuned topass this intermediate frequency and the intermediate amplifier 40 istuned to amplify it in any well known manner.

Referring to Figs. 2 to 8, the selector coil [0 is wound on aninsulating tube 50 which has an enlarged end 5| and which preferablypasses through a slotted opening 52 in a bracket 53 and is adjustablyheld in place by a spring 54 which has a divided anchoring means 54which snaps 55 through a hole 54 in the bracket to lock the spring tothe bracket. The bracket 53 is adjus-tably mounted on a frame 55 and hasa base 53 which slides on the frame and which has a finger 53 extendinginto a slot 55 which is formed by striking up a tongue 55. This tonguepasses through an opening 53 in the bracket, the tongue having a curvedend which presses the base 53* against the frame. The finger 53 and thetongue serve to guide the bracket so as to give it a parallel motion.

The oscillator coil H is similarly wound or otherwise mounted on aninsulating tube 51 which has an enlarged end 58 which is pressed againstthe metal end 59 of the frame by means of a spring 69 which ispreferably a duplicate of the spring 54. The end 59 is secured to theframe 54 by means of screws 59 and is threaded to receive a screw 5! theend of which is preferably made hollow to receive a wire rod 62 whichextends axially through both of the insulating tubes 59 and 51 and ispressed toward the screw 6! by means of a spring 63. The rod 62 carriestwo magnetic cores 64, 55 which are preferably made of very finelydivided magnetic dust which is molded with a suitably insulating bond.This arrangement provides a very simple and efficient means for mountingthe coils and for adjusting the frequency of each coil separately aswill hereinafter be described.

An edge of the base of the bracket is provided with a series of smallserrations 53 which overlie an openin 54 in the frame which preferablyhas larger serrations so that a flat instrument A such as the point of asmall screw driver can be inserted and by rotating this instrument, asshown in Fig. 5, the bracket can be moved back and forth thereby movingthe coil Iii with respect to its core 64 thereby adjusting the frequencyof the selector coil Ill By moving the screw 5| the frequencies of boththe selector coil Iii and the oscillator coil ll are simultaneouslyadjusted. In practice, the frequency of the oscillator coil H will firstbe adjusted by means of the screw 6| to a desired frequency as that of astation in the broadcast field, after which the selector coil Ill willbe adjusted by means of the instrument A to the same frequency. Afterthis, any movement of the screw 6! will simultaneously adjust both theselector and oscillator coils and in substantially the same amounts sothat an operator can readily adjust the frequency of a pair of selectorand oscillator coils as I0 I l from one station to another stationhaving a nearby frequency. Where, however, a number of such pairs ofcoils, say six such pairs, were to be made applicable to a fairly widerange of frequencies, such as occurs in the broadcast field, two of suchpairs would be wound for the low portion of the desired range, two forthe intermediate portion, and two for the high frequency portion.

Over each pair of such coils is preferably mounted a plunger 66 whichhas an operating button 61 which preferably carries in its face a diskwith the call letters of the broadcast station to whose frequency its.coils are tuned. This plunger is normally held outwardly by means of aspring 68 and when pressed inwardly to the position 65 is caught andheld by a pawl 69 which is pressed toward the plunger by means of a leafspring Hi. This pawl is so arranged that as each plunger advances, itreleases the pawl so as to release any plunger which is held.

The plunger 66 when pushed in closes the switches l3 and 23 of Fig. 1.These switches form no part of the present invention and hence will notbe described in detail.

Another selector coil like coil I b may be added and operated by a corelike 64 on the rod 62 to give an added preselector stage of radiofrequency amplification if desired.

From the foregoing it will be clear that this provides a very simple andcompact form of radio receiver and one wherein a single fixed capacitorserves to form with each of a series of inductances a resonant circuitof a predetermined frequency. It will be noted that the adjustment forfrequencies of the several circuits is accomplished without the use ofeither a Variable condenser for this purpose or even of a trimmercondenser.

We claim:

1. In a radio receiving set, a variable high-frequency inductance devicecomprising a frame, an insulating sleeve, spring means yieldinglyclamping the sleeve to the frame, a movable bracket slidably mounted onthe frame and movable axially of the sleeve and coil, a secondinsulating sleeve mounted on the bracket in axial alignment with thefirst-mentioned sleeve and movable with the bracket, an oscillator coilmounted on one of said sleeves, a selector coil mounted on the othersleeve and electrically connected to the oscillator coil, a core formedof magnetic material mounted for sliding movement in each sleeve, meansmechanically connecting said cores for shifting the axial positions ofthe latter within their respective sleeves in unison, means preventinglateral shifting of the bracket on the frame, a series of serrationsformed on the bracket and a series of opposed serrations formed on theframe and spaced from the former serrations, said serrations beingdesigned to cooperate with a tool for shifting of the bracket axially ofthe sleeves and cores.

2. In a radio receiving set, a variable high-fre quency inductancedevice comprising a frame, an insulating sleeve, spring means yieldinglyand dctachably clamping the sleeve to the frame, a movable bracketslidably mounted on the frame and movable axially of the sleeve andcoil, a second insulating sleeve, spring means yieldably and detachablyclamping said latter sleeve to the bracket in axial alignment with thefirst-mentioned sleeve whereby the latter sleeve is rncvable withbracket, an oscillator coil mounted on one of said sleeves, a selectorcoil mounted on the other sleeve electrically connected to theoscillator coil, a rod extending axially through both sleeves, amagnetic core secured to said rod within each sleeve, spring meansnormally urging the rod to a limiting position in one direction, andmeans on said frame determining the limiting position of the rod and forshifting the rod axially in the other direction.

3. In a radio receiving set, a variable high-frequency inductance devicecomprising a frame, an insulating sleeve, spring means yieldingly anddetachably clamping the sleeve to the frame, a movable bracket slidablymounted on the frame and movable axially of the sleeve and coil, asecond insulating sleeve, spring means yieldably and detachably clampingsaid latter sleeve to the bracket in axial alignment with thefirst-mentioned sleeve whereby the latter sleeve is movable with thebracket, an oscillator coil mounted on one of said sleeves, a selectorcoil mounted on the other sleeve and electrically connected to theoscillator coil, a rod extending axially through both sleeves, amagnetic core secured to said rod within each sleeve, and means on saidframe for shifting the position of the rod axially of the sleeves,

4. In a radio receiving set, a variable high-frequency inductance devicecomprising a frame, an insulating sleeve, spring means yieldingly anddetachably clamping the sleeve to the frame, a movable bracket slidablymounted on the frame and movable axially of the sleeve and coil, asecond insulating sleeve, spring means yieldably and detachably clampingsaid latter sleeve to the bracket in axial alignment with thefirst-mentioned sleeve whereby the latter sleeve is movable with thebracket, an oscillator coil mounted on one of said sleeves, a selectorcoil mounted on the other sleeve and electrically connected to theoscillator coil, a rod extending axially through both sleeves, amagnetic core secured to said rod within each sleeve, means on saidframe for shifting the position of the rod axially of the sleeves, andcooperating means on the frame and movable bracket designed forengagement with a tool in shifting the position of the bracket relativeto the frame.

5. In a radio receiving set, a variable high-frequency inductance devicecomprising a frame, an insulating sleeve, spring means yieldingly anddetachably clamping the sleeve to the frame, a movable bracket slidablymounted on the frame and movable axially of the sleeve and coil, asecond insulating sleeve, spring means yieldably and detachably clampingsaid latter sleeve to the bracket in axial alignment with thefirst-mentioned sleeve whereby the latter sleeve is movable with thebracket, an oscillator coil mounted on one of said sleeves, a selectorcoil mounted on the other sleeve and electrically connected to theoscillator coil, a rod extending axially through both sleeves, amagnetic core secured to said rod within each sleeve, spring meansnormally urging the rod to a limiting position in one direction, meanson said frame determining the limiting position of the rod and forshifting the rod axially in the other direction, and cooperating meanson the frame and movable bracket designed for engagement with a tool inshifting the position of the bracket relative to the frame.

HAR'IMAN B. CANON. JESSE H. CLARK.

